Not entirely true. Double Fine has remastered 3 of the classic LucasArts point-and-click adventure games, including Grim Fandango. Alongside Full Throttle and Day of the Tentacle. Not to mention they created an original title called Broken Age.
And with Monkey Island making its triumphant return this year with nearly the entire original leads, minus Tim, there could be hope for Grim Fandango 2. Although, idk if Double Fine outright bought the Grim IP from Lucasfilm or they just bought the rights to remastering the original game.